.TH std::setbase 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::setbase \- std::setbase

.SH Synopsis
   Defined in header <iomanip>
   /*unspecified*/ setbase( int base );

   Sets the numeric base of the stream. When used in an expression out << setbase(base)
   or in >> setbase(base), changes the basefield flag of the stream out or in,
   depending on the value of base:

     * the value 16 sets basefield to std::ios_base::hex.
     * the value 8 sets std::ios_base::oct.
     * the value 10 sets std::ios_base::dec.

   Values of base other than 8, 10, or 16 reset basefield to zero, which corresponds to
   decimal output and prefix-dependent input.

.SH Parameters

   base - new value for basefield

.SH Return value

   An object of unspecified type such that

     * if out is an object of type std::basic_ostream<CharT, Traits>, the expression
       out << setbase(base)
          * has type std::basic_ostream<CharT, Traits>&
          * has value out
          * behaves as if it called f(out, base)
     * if in is an object of type std::basic_istream<CharT, Traits>, the expression in
       >> setbase(base)
          * has type std::basic_istream<CharT, Traits>&
          * has value in
          * behaves as if it called f(in, base)

   where the function f is defined as:

 void f(std::ios_base& str, int base)
 {
     // set basefield
     str.setf(base == 8 ? std::ios_base::oct :
         base == 10 ? std::ios_base::dec :
         base == 16 ? std::ios_base::hex :
         std::ios_base::fmtflags\fB(0)\fP, std::ios_base::basefield);
 }

.SH Example


// Run this code

 #include <iomanip>
 #include <iostream>
 #include <sstream>

 int main()
 {
     std::cout << "Parsing string \\"10 0x10 010\\"\\n";

     int n1, n2, n3;
     std::istringstream s("10 0x10 010");

     s >> std::setbase(16) >> n1 >> n2 >> n3;
     std::cout << "hexadecimal parse: " << n1 << ' ' << n2 << ' ' << n3 << '\\n';

     s.clear();
     s.seekg(0);

     s >> std::setbase(0) >> n1 >> n2 >> n3;
     std::cout << "prefix-dependent parse: " << n1 << ' ' << n2 << ' ' << n3 << '\\n';

     std::cout << "hex output: " << std::setbase(16)
               << std::showbase << n1 << ' ' << n2 << ' ' << n3 << '\\n';
 }

.SH Output:

 Parsing string "10 0x10 010"
 hexadecimal parse: 16 16 16
 prefix-dependent parse: 10 16 8
 hex output: 0xa 0x10 0x8

   Defect reports

   The following behavior-changing defect reports were applied retroactively to
   previously published C++ standards.

     DR    Applied to          Behavior as published          Correct behavior
   LWG 183 C++98      setbase could only be used with streams usable with any
                      of type std::ostream or std::istream    character stream

.SH See also

   dec        changes the base used for integer I/O
   hex        \fI(function)\fP
   oct
   showbase   controls whether prefix is used to indicate numeric base
   noshowbase \fI(function)\fP
